This is a phase II randomized study of the antiviral activity and resistance interactions of lamivudine (3TC) in combination with zidovudine (ZDV) stavdine (D4T) or didanosine (DDI) versus monotherapy with DDI or D4T in HIV infected individuals with 200-600 CD4 + cells/mm3 and no previous nucleoside experience. Enrollment into this trial is proceeding.